题目

Dear Lingling，I am writing this letter to you in my classroom.It's really a big room.There are fifty students in my class，twenty­eight girls and twenty­two boys.In the front of the classroom，there is a blackboard，a map of the world and a desk for our teachers.On the teacher's desk，there is a computer.Around the classroom，there are four windows in the wall.We all like our classroom.What's your classroom like？Please write to me.Yours，Betty【1】How many boys are there in Betty's class?A.Fifty. B.Twenty. C.Twenty­eight. D.Twenty­two.【2】What's in the front of the classroom向量，设函数.(1)求的最小正周期与单调递减区间；(2)在中，分别是角的对边，若的面积为，求的值.